Atmospheric refraction bends a ray through the vertical refractive index gradient, shifting its apparent direction. Because of optical dispersion, the shift varies with wavelength.
Atmospheric dispersion is the wavelength dependence of atmospheric refraction. It spreads a broadband stellar image along the vertical direction toward the zenith.
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Atmospheric refraction is the bending of light as it passes through the Earth's atmosphere. This phenomenon occurs because the atmosphere is not a uniform medium; instead, it has varying densities and temperatures, which can change how light travels through it. When light waves enter the atmosphere from space, they encounter layers of air with different properties, primarily due to temperature gradients.